The expression $100 + 20m$ gives the volume of water in Eduardo's pool (in liters) after Eduardo spends $m$ minutes filling his pool. What is the volume of water in Eduardo's pool after he fills it for $5 \dfrac14$ minutes?
Explanation: Eduardo fills his pool for ${5 \dfrac14}$ minutes, so $m={5\dfrac14}$. Let's substitute $m={5\dfrac14}$ into the expression and evaluate: $\begin{aligned} &\phantom{=}100 + 20m\\\\ &= 100 + 20\left({5\dfrac14}\right)\\\\ &= 100+105\\\\ &={205} \end{aligned}$ Eduardo's pool will have ${205}$ liters of water after he fills it for ${5\dfrac14}$ minutes.